# Volatility
# Copyright (C) 2007-2013 Volatility Foundation
#
# This file is part of Volatility.
#
# Volatility is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Volatility is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Volatility.  If not, see <http://www.gnu.org/licenses/>.
#

"""
@author:       Andrew Case
@license:      GNU General Public License 2.0
@contact:      atcuno@gmail.com
@organization: 
"""

import volatility.obj as obj
import volatility.debug as debug

import volatility.plugins.linux.common as linux_common
import volatility.plugins.linux.pslist as linux_pslist

PIDTYPE_PID = 0

# determining the processing algorithm to use is based on crash from redhat
class linux_pidhashtable(linux_pslist.linux_pslist):
    """Enumerates processes through the PID hash table"""

    def __init__(self, *args, **kwargs):
        self.seen_tasks = {}
        linux_pslist.linux_pslist.__init__(self, *args, **kwargs)

    def get_obj(self, ptr, sname, member):
        offset = self.profile.get_obj_offset(sname, member)
        addr   = ptr - offset
        return obj.Object(sname, offset = addr, vm = self.addr_space)

    def _task_for_pid(self, upid, pid):

        chained = 0

        pid_tasks_0 = pid.tasks[0].first

        if pid_tasks_0 == 0:
            chained = 1
            pnext_addr = upid.obj_offset + self.profile.get_obj_offset("upid", "pid_chain") + self.profile.get_obj_offset("hlist_node", "next")
            pnext = obj.Object("unsigned long", offset = pnext_addr, vm = self.addr_space)
            upid = obj.Object("upid", offset = pnext - self.profile.get_obj_offset("upid", "pid_chain"), vm = self.addr_space)
            for task in self._walk_upid(upid):
                yield task

        if chained == 0:
            task = obj.Object("task_struct", offset = pid_tasks_0 - self.profile.get_obj_offset("task_struct", "pids"), vm = self.addr_space)
            if task.pid > 0:
                yield task

    def _walk_upid(self, upid):

        while upid:

            pid = self.get_obj(upid.obj_offset, "pid", "numbers")

            for task in self._task_for_pid(upid, pid):
                yield task

            if type(upid.pid_chain) == obj.Pointer:
                pid_chain = obj.Object("hlist_node", offset = upid.pid_chain.obj_offset, vm = self.addr_space)
            else:
                pid_chain = upid.pid_chain

            if not pid_chain:
                break

            upid = self.get_obj(pid_chain.next, "upid", "pid_chain")

    def _get_pidhash_array(self):
        pidhash_shift = obj.Object("unsigned int", offset = self.addr_space.profile.get_symbol("pidhash_shift"), vm = self.addr_space)
        pidhash_size = 1 << pidhash_shift

        pidhash_addr = self.addr_space.profile.get_symbol("pid_hash")
        pidhash_ptr = obj.Object("Pointer", offset = pidhash_addr, vm = self.addr_space)

        # pidhash is an array of hlist_heads
        pidhash = obj.Object(theType = 'Array', offset = pidhash_ptr, vm = self.addr_space, targetType = 'hlist_head', count = pidhash_size)

        return pidhash

    def calculate_v3(self):
        self.seen_tasks = {}

        pidhash = self._get_pidhash_array()

        for hlist in pidhash:
            # each entry in the hlist is a upid which is wrapped in a pid
            ent = hlist.first

            while ent.v():
                upid = self.get_obj(ent.obj_offset, "upid", "pid_chain")

                for task in self._walk_upid(upid):
                    if not task.obj_offset in self.seen_tasks:
                        self.seen_tasks[task.obj_offset] = 1
                        if task.is_valid_task():
                            yield task

                ent = ent.m("next")

    # the following functions exist because crash has handlers for them
    # but I was unable to find a profile/kernel that needed them (maybe too old or just a one-off distro kernel
    # if someone actually triggers this message, I can quickly add in the support as I will have a sample to test again
    def profile_unsupported(self, func_name):
        debug.error("{0:s}: This profile is currently unsupported by this plugin. Please file a bug report on our issue tracker to have support added.".format(func_name))

    def calculate_v2(self):
        poff = self.addr_space.profile.get_obj_offset("task_struct", "pids") 

        pidhash    = self._get_pidhash_array()

        for p  in pidhash:
            if p.v() == 0:
                continue
            
            ptr = obj.Object("Pointer", offset = p.v(), vm = self.addr_space)
    
            if ptr.v() == 0:
                continue

            pidl = obj.Object("pid_link", offset = ptr.v(), vm = self.addr_space)

            nexth = pidl.pid

            if not nexth.is_valid():
                continue
         
            nexth = obj.Object("task_struct", offset = nexth - poff, vm = self.addr_space)

            while 1:
                if not pidl:
                    break

                yield nexth
               
                pidl = pidl.node.m("next").dereference_as("pid_link")    
                
                nexth = pidl.pid

                if not nexth.is_valid():
                    break
 
                nexth = obj.Object("task_struct", offset = nexth - poff, vm = self.addr_space)

    def calculate_v1(self):
        self.profile_unsupported("calculate_v1")

    def refresh_pid_hash_task_table(self):
        self.profile_unsupported("refresh_pid_hash_task_table")

    def get_both(self):
        has_pid_link = self.profile.has_type("pid_link")
        has_link_pid = self.profile.obj_has_member("pid_link", "pid")

        has_pid_hash = self.profile.has_type("pid_hash")
        has_upid = self.profile.has_type("upid")
        has_pid_numbers = self.profile.obj_has_member("pid", "numbers")

        if has_pid_hash:
            has_hash_chain = self.profile.obj_has_member("pid_hash", "chain")
        else:
            has_hash_chain = None

        if has_link_pid and has_hash_chain:
            func = self.refresh_pid_hash_task_table

        elif has_pid_link:
            if has_upid and has_pid_numbers:
                func = self.calculate_v3 # refresh_hlist_task_table_v3
            else:
                func = self.calculate_v2 # refresh_hlist_task_table_v2
        else:
            func = self.calculate_v1

        return func

    def determine_func(self):
        pidhash = self.addr_space.profile.get_symbol("pidhash")
        pid_hash = self.addr_space.profile.get_symbol("pid_hash")
        pidhash_shift = self.addr_space.profile.get_symbol("pidhash_shift")

        if pid_hash and pidhash_shift:
            func = self.get_both()

        elif pid_hash:
            func = self.refresh_pid_hash_task_table

        elif pidhash:
            func = self.refresh_pid_hash_task_table

        return func

    def calculate(self):
        linux_common.set_plugin_members(self)
        func = self.determine_func()

        for task in func():
            yield task






